1. Technical Field
The present invention relates to wireless communications, and more particularly, to a method of transmitting and receiving a frame to be multicast and/or broadcast in a wireless local area network (WLAN) system and an apparatus supporting the method.
2. Related Art
With the advancement of information communication technologies, various wireless communication technologies have recently been developed. Among the wireless communication technologies, a wireless local area network (WLAN) is a technology whereby Internet access is possible in a wireless fashion in homes or businesses or in a region providing a specific service by using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc.
The IEEE 802.11n is a technical standard relatively recently introduced to overcome a limited data rate which has been considered as a drawback in the WLAN. The IEEE 802.11n is devised to increase network speed and reliability and to extend an operational distance of a wireless network. More specifically, the IEEE 802.11n supports a high throughput (HT), i.e., a data processing rate of up to above 540 Mbps, and is based on a multiple input and multiple output (MIMO) technique which uses multiple antennas in both a transmitter and a receiver to minimize a transmission error and to optimize a data rate.
With the widespread use of the WLAN and the diversification of applications using the WLAN, there is a recent demand for a new WLAN system to support a higher throughput than a data processing rate supported by the IEEE 802.11n. A next-generation WLAN system supporting a very high throughput (VHT) is a next version of the IEEE 802.11n WLAN system, and is one of IEEE 802.11 WLAN systems which have recently been proposed to support a data processing rate of above 1 Gbps in a MAC service access point (SAP).
To effectively utilize a radio channel, the next-generation WLAN system supports multi user-multiple input multiple output (MU-MIMO) transmission in which a plurality of non-access point (AP) stations (STAs) concurrently access to a channel. According to the MU-MIMO transmission, an AP can transmit a frame concurrently to one or more MIMO-paired STAs.
Meanwhile, in a WLAN system, a transmission AP and/or a transmission STA support transmission and/or reception of a multicast/broadcast frame in a unicast manner. This is called a directed multicast service (DMS). By using the DMS, the transmission AP and/or the transmission STA can transmit the multicast/broadcast frame to a specific reception STA.
The multicast/broadcast frame can be intended to be transmitted simultaneously to a plurality of reception STAs while transmitting the frame in the unicast manner. This is because in doing so, reliability and an overall throughput of the WLAN system can be improved. For this, there is an on-going attempt to transmit and receive the multicast/broadcast frame by using a MU-MIMO transmission scheme.